1. Field of the Invention
The present invention relates to an agitation mixer in which a raw material is heat-fused or enhanced in fluidity using steam, and relates to a pasteurizer and a cleaning device using steam.
2. Description of the Related Art
In general, when a raw material is fused or dissolved by means of heating, a solvent used for dissolution is supplied into a tank with an agitator in advance or concurrently with feeding of the powder, and then mixed with the powder.
In this method, however, because undissolved substances (i.e. agglomerates or lumps) of the powder are dispersed in the solvent, high volumes of solvent and/or lengthy periods of time are inevitably expended for uniform fusion or uniform dissolution.
For example, when a film is formed by dissolving a polyvinyl alcohol series resin in a solvent and then preparing a resulting undiluted solution through mixing and deaeration, disadvantages that undissolved substances remain due to poor agitation and that distribution of concentration is non-uniform in the solution containing the polyvinyl alcohol series resin can develop during generation of a high concentration of the undiluted solution, which brings about difficulties in controlling the concentration of the undiluted solution to be uniform.
In view of the aforesaid problem, there is suggested a method of preparing an aqueous solution of vinyl alcohol series resin, the method in which a wet cake of hydrated polyvinyl alcohol series resin is dissolved in a dissolver canister with an impeller blade for generating vertical reflux while blowing steam into the dissolver canister (refer to, for example, Japanese Patent Laid-Open Publication No. 2002-60495, No. 2002-59474, No. 2002-59475, and No. 2002-62429).
When the aqueous solution of vinyl alcohol series resin is produced by injecting steam into the wet cake of hydrated polyvinyl alcohol series resin in the dissolver canister (for example, a tank) having the impeller blade as described above, a lengthy period of time is spent for dissolution of the hydrated polyvinyl alcohol series resin.